Today, a large number of virtual machines (VMs) are served by a single LUN and it's difficult, if not impossible, to get data management at the granularity of a VM. For example, if one VM is hogging resources, it takes a lot of effort from the storage administrator to determine which VM is causing the problem. Another issue with this LUN-level granularity is that all VMs contained within a LUN get the same data services, such as snapshots, replication, cloning, encryption and data deduplication, whether they need to or not. Virtual Volumes change this so storage can be provisioned to an independent VM that can then be assigned only the data services required. Assignment of the right storage resources is accomplished using Storage Policy Based Management, which simplifies both provisioning and the day-to-day management of VMs in a significant way. Because VMware VVOLs are still a new feature, here are five items to keep in mind:

Takeaway 1: VVOLs coexist with VMFS and VSAN

Because VVOLs work alongside VMware's Virtual Machine File System (VMFS) and Virtual SAN (VSAN), wholesale infrastructure changes are not necessary. You can have some applications running as VMs that use the old style and are served by VMFS, some that use VSAN (direct-attached storage) and others that use VVOLs. It is possible to partition an external storage array and allocate one portion as LUNs for VMFS and another for VVOLs. VMware ensured VVOLs are conceptually disruptive but evolutionary at the implementation level.

Takeaway 2: Major development work is needed

Work is still needed on the storage array side to support VMware’s VVOLs. How difficult it will be depends on the architecture of the storage array. Don't expect your favorite storage array to support VVOLs on the same day vSphere 6 ships. Each vendor has a plan to support VVOLs over time and it is done model by model. Be sure you know not only that your supplier supports VVOLs, but which models it supports or on what timeline it is planning support. It's important to note that support for VVOLs is not automatic for all the other infrastructural software you purchase optionally today.

Takeaway 3: VMware VVOLs support all major storage protocols

I'm referring to Fibre Channel, iSCSI and NFS. VMware has done this by using a concept called Protocol Endpoints, which makes the interaction between ESXi and storage look exactly as it did in the world of LUNs. I have not seen CIFS (SMB) or InfiniBand support listed anywhere. If those protocols are important to your installation, you should check with your supplier.

Takeaway 4: VVOLs do not make storage vendors equal

It's a mistake to think VVOLs are an equalizer of storage from different vendors. Storage offers a dizzying array of differentiation in almost all dimensions: performance, provisioning, deployment, caching, tiering, availability, virtualization, data protection and the elegance/efficiency of data services. Each storage vendor is clamoring to state that it supports VMware VVOLs; but the devil is in the details. One product may only support provisioning at the VM level but management is still at the LUN level. Another might support provisioning but the data services supported under VVOLs is an incomplete list. There may be a limit on the total number of VVOLs supported by the array or similar restrictions. You'll need to ask your supplier the difficult questions to know exactly what is supported and when.

Takeaway 5: VVOLs don't provide vendor quality of service

Don't believe for a second that vendors who already support VM-level granularity or offer quality of service (QoS) functionality at the VM level will lose that differentiation. It's a common fallacy to assume that VVOLs give QoS to the array that supports it. Nothing could be further from the truth. If the array never had QoS to begin with, it will not have it now. Vendors such as Maxta, NexGen, Nutanix, SimpliVity, Tintri and others will continue to enjoy differentiation in the post-VVOLs era. Yes, the provisioning and possibly the management portion will probably become commoditized over time, but the same isn't true for other aspects of their feature sets.

Expect more VVOLs support over the next year

VMware VVOLs help to fix the mismatch between the VM and storage worlds by allowing them to be viewed through a common lens. This will have serious benefits for all parties concerned: IT administrators, VMware admins and end users. Even application admins will find benefits, as application performance issues will be much easier to diagnose and resolve.

VVOLs came on the market just as users need to manage thousands, and often tens of thousands, of VMs. But vendor support of VVOLs will vary, and it will likely take the next 18 months to arrive at any state of equilibrium where most products will have at least rudimentary support of the technology

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